Optical projection apparatus with normal illumination means



H. M. E. PASQUET v 2,496,675 OPTICAL PROJECTION APPARATUS WITH NORMAL ILLUMINATION MEANS Filed June 18, 194e Feb. 7, H950 /A/l//VT www; magfdmdf Patented Feb. 7, 1950 OPTICAL PROJ ECTION APPARATUS WITH NORMAL ILLUMINATION MEANS Henri Marcel Edmond Pasquet, Neullysur-Seine,

France, assigner to Societe dApplications Generales DElectricite & De Mecanique, Sagem, Paris, France, a society of France Application .I une 18, 1946, Serial No. 677,612 In France May 22, 1946 2 claims. (el. sas-24) The present invention relates to optical ap paratus for the examination of an artificially illuminated object, either directly or by pho tography, and in particular after optical enlarging thereof, the invention being more especially, although not exclusively, concerned with apparatus of this type giving on a screen an enlarged projection of the image.

The chief object of my invention is to provide an apparatus of this type which is better adapted to meet the requirements of practice than those used for the same purpose up to the present time.

Preferred embodiments of my invention will be hereinafter described with reference to the accompanying drawings, given merely by Way of example, and in which:

The only figure is a diagrammatical View of an enlarging apparatus made according to an embodiment of my invention.

This apparatus comprises on the one hand, means for concentrating the light flux from an illuminating source 2 on an observation area 3, of substantially flat shape, on Which is disposed the object to be examined, and on the other hand, optical means for examination of this object, to Wit, in this case, means for projecting this object on screen 4.

According to my invention, the observation area 3 being transverse, and preferably perpendicular, to the line that joins it to the light source 2, the light flux concentrating means essentially include a reflector extending around said source and shaped to defiect the light rays emitted from said source transversely to said line into directions making small angles therewith, said directions preferably converging toward said area 3 so as further to increase the light concentration thereon.

Advantageously, as shown by the drawings, reector l is given the shape of the portion of a quadric surface that laterally surrounds source 2, the latter being located in one of the focal regions of this surface While area 3 is located in the other focal region thereof and is advantageously perpendicular to the focal axis thereof.

Thus, the light flux reflected from the object to be examined in directions close to the normal to surface 3 is very intensive and can be usefully caught by the optical system serving to the formation on screen 4 of an enlarged image of this object.

It Will be readily understood that such an apparatus permits of utilizing most of the ux emitted by illuminating source 2. Therefore it 2 will be possible to make use of a source of relatively low brightness, that is to say producing heat radiations which do not risk deteriorating or deforming the object in question.

Furthermore, due to the fact that the light beam reiiected from this object is substantially at right angles to the observation surface 3, accommodation of the receiving optical system to the points of said object that are most distant from one another vvill take place under much more favorable conditions than in the case of apparatus in which the reflected beam is oblique. In other words, the detrimental effects of distortion and the defect of sharpness of the marginal portions of the image will thus be reduced to a minimum.

Advantageously, the illuminating source 2 is constituted by a high gaseous pressure mercury vapor lamp, emitting light rays from a surface of cylindrical shape. One of the characteristic features of such a lamp is that it supplies practically no light rays in the axial direction of said cylindrical surface.

Advantageously, reflector I is constituted by a portion of an ellipsoid of revolution the eccentricity of which is the greater as it is desired to obtain an illuminating beam contained in a smaller solid angle. In some cases, reflector I may be given the shape of a paraboloid of revolution having its axis at right angles to surface 3.

In some cases, when it is desired to obtain an oblong illuminated area on surface 3, for instance when the objects to 'be examined are themselves of oblong shape, reflector i, instead of being in the shape of a body of revolution, Will be given any suitable elongated shape in transverse section, i. e. in section by planes perpendicular to the axial line joining the central point of area 6 with the source of light. But in al1 cases, the sections of the surface of this reflector by planes passing through this axial line must be conical curves having their focus in the region of source 2.

Advantageously, the illuminating element of this source has an elongated shape and extends along said axial line. For instance, when, as above mentioned, the source is a mercury vapo-r lamp having an illuminating element of cylindrical shape, this element is coaxial With reflector l.

According to my invention, the optical means for receiving the light beam emitted from the object to be examined is disposed between source 2 and surface 3. The optical axis of said means is to coincide with the optical axis of reiiector i.

In the example shown by the drawing, the optical means in question includes a magnifying objective system 5 and a prism or mirror E for deflecting the light rays, for instance through a tube l the-Walls`ofwhich are.,preferably blackened, onto aimirror 8 from which these rays are. finally projected on screen 4.

In addition to these elements, the apparatus-x according to my invention preferably further includes means for subjecting" the illuminating; means to an anamorphosis and/orto a selectiveA treatment for eliminating certain radiations.'

For instance, as shown bythedrawing, an.an.- nular lens 9, which surrounds-:objestivesystemii;l concentrates the light beam from reector I onto surface 3.

Suitable lters may be incorporated in thelsys.- tem to exert the desired selective action above referred to, for instance for stopping longfwave length rays which mightiproduce heat radiation. a

Of course; the anamorphosis: and/or, selective: means are advantageously mounted in aremoV-eable' or. adjustable manner; so as; to` permitv of: examining pieces` under diierent illuminating conditions.

As .for screenr it isadvantageously constituted? by a plane=surface; eitheropaque. orxtranslucent, eventually coated Withf. a fluorescent product'.- Bnt this does not exclude.=-tl1e possibility of em-VA ploying curvilinear: screens? forfthe; examinatiow of. objects# having; curvedisurfacesf (balls,r rods;-` wires,; etcr) .l

Itis to, improvev the'fsharpness ofthe imagefoff an: object, the surfacei'oiwhichis,to be examined, that the-Objectis located in a-plurality of differ.m ent planes by immersing said. objectfln. a, liquid` having a lhigh-index ofi refraction:

Thev apparatus according Yto :the present ini/ene` tion has manyadva-ntages? amongwhich. the foielowingfmay be considered'fas particularly impera tantz' It permits of obtainingpimages that? are clearly-`V visible even in daylight, Without. subjecting'theobject that' is: examined; tothe effect of` dangerouszcaloric radiations;

Theiimage's that'a-re obtained; arefuniformly il-y luminated, in particular owingl to'thelocaton oi-fv the; objective system in a. neutral. zone, that is;l to say in conditionssuclrthatnol shadow is pro-w jected onto thee zone'f-of,` observation;

sharpness: also-is*practically` uniform,v even in the marginal zones: and. with objective systems ofrlowA accommodation power, owing to the fact! that the' reected.; beam Aissubstantiailyl perpen dicular tozthe planei of. theeobject.

`It is-` pointedout that the inventionjsi not lim.-`

' comprises; inf combination, means forming an observation.. arear for. an object, an illuminating souncezfofelongatedshape extending along a portion of an axis at least Substantially at right anglestosaid area, the length of said source along said axis being of the same order of magnitude astice-radius of saidarea; meansforiconcentrating onto "aidarea substantiallyfallthe-light.rays-v frownl source with the. exceptionv ot those` making-ga,- ver y smallfanglefwith saidl axis,K said.` means including a` reflector coaxially.'surround=-- ing saidsource and.. the-faXia'lf-seotionsof-.Which-l are portions-off-ellipsesr having one focus-onsaid; source the other one; in.. ther? region ofsaid area: and magnifying means; forexaminaticn of said-object'including aniobjective system located along' saidaxistbetween.saidsourceandsaidffarea.

2'. An apparatus according to'claim. 1 .in,;whichs the illuminating source is a high gaseous-@pressure mercury vapor lamp, thef light ernitting-v element of v`whichis a, cylinder locatedi along said axis;

HENRI MARCEL EDMONDvR-ASQUET.

REFERENCES CITEDr The following referencesarefof recorddngthee leof this patent:

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